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1 | @c Copyright 1991, 1992, 1993, 1994, 1995, 1997, 1999, 2000, 2001, |
2 | @c 2002, 2003, 2004 | |
f7e42eb4 | 3 | @c Free Software Foundation, Inc. |
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4 | @c This is part of the GAS manual. |
5 | @c For copying conditions, see the file as.texinfo. | |
6 | @ifset GENERIC | |
7 | @page | |
8 | @node MIPS-Dependent | |
9 | @chapter MIPS Dependent Features | |
10 | @end ifset | |
11 | @ifclear GENERIC | |
12 | @node Machine Dependencies | |
13 | @chapter MIPS Dependent Features | |
14 | @end ifclear | |
15 | ||
16 | @cindex MIPS processor | |
17 | @sc{gnu} @code{@value{AS}} for @sc{mips} architectures supports several | |
84ea6cf2 | 18 | different @sc{mips} processors, and MIPS ISA levels I through V, MIPS32, |
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19 | and MIPS64. For information about the @sc{mips} instruction set, see |
20 | @cite{MIPS RISC Architecture}, by Kane and Heindrich (Prentice-Hall). | |
21 | For an overview of @sc{mips} assembly conventions, see ``Appendix D: | |
22 | Assembly Language Programming'' in the same work. | |
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23 | |
24 | @menu | |
25 | * MIPS Opts:: Assembler options | |
26 | * MIPS Object:: ECOFF object code | |
27 | * MIPS Stabs:: Directives for debugging information | |
28 | * MIPS ISA:: Directives to override the ISA level | |
aed1a261 | 29 | * MIPS symbol sizes:: Directives to override the size of symbols |
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30 | * MIPS autoextend:: Directives for extending MIPS 16 bit instructions |
31 | * MIPS insn:: Directive to mark data as an instruction | |
32 | * MIPS option stack:: Directives to save and restore options | |
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33 | * MIPS ASE instruction generation overrides:: Directives to control |
34 | generation of MIPS ASE instructions | |
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35 | @end menu |
36 | ||
37 | @node MIPS Opts | |
38 | @section Assembler options | |
39 | ||
40 | The @sc{mips} configurations of @sc{gnu} @code{@value{AS}} support these | |
41 | special options: | |
42 | ||
43 | @table @code | |
44 | @cindex @code{-G} option (MIPS) | |
45 | @item -G @var{num} | |
46 | This option sets the largest size of an object that can be referenced | |
47 | implicitly with the @code{gp} register. It is only accepted for targets | |
48 | that use @sc{ecoff} format. The default value is 8. | |
49 | ||
50 | @cindex @code{-EB} option (MIPS) | |
51 | @cindex @code{-EL} option (MIPS) | |
52 | @cindex MIPS big-endian output | |
53 | @cindex MIPS little-endian output | |
54 | @cindex big-endian output, MIPS | |
55 | @cindex little-endian output, MIPS | |
56 | @item -EB | |
57 | @itemx -EL | |
58 | Any @sc{mips} configuration of @code{@value{AS}} can select big-endian or | |
59 | little-endian output at run time (unlike the other @sc{gnu} development | |
60 | tools, which must be configured for one or the other). Use @samp{-EB} | |
61 | to select big-endian output, and @samp{-EL} for little-endian. | |
62 | ||
63 | @cindex MIPS architecture options | |
64 | @item -mips1 | |
65 | @itemx -mips2 | |
66 | @itemx -mips3 | |
67 | @itemx -mips4 | |
84ea6cf2 | 68 | @itemx -mips5 |
e7af610e | 69 | @itemx -mips32 |
af7ee8bf | 70 | @itemx -mips32r2 |
84ea6cf2 | 71 | @itemx -mips64 |
5f74bc13 | 72 | @itemx -mips64r2 |
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73 | Generate code for a particular MIPS Instruction Set Architecture level. |
74 | @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors, | |
75 | @samp{-mips2} to the @sc{r6000} processor, @samp{-mips3} to the | |
84ea6cf2 | 76 | @sc{r4000} processor, and @samp{-mips4} to the @sc{r8000} and |
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77 | @sc{r10000} processors. @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, |
78 | @samp{-mips64}, and @samp{-mips64r2} | |
79 | correspond to generic | |
80 | @sc{MIPS V}, @sc{MIPS32}, @sc{MIPS32 Release 2}, @sc{MIPS64}, | |
81 | and @sc{MIPS64 Release 2} | |
82 | ISA processors, respectively. You can also switch | |
584da044 | 83 | instruction sets during the assembly; see @ref{MIPS ISA, Directives to |
ec68c924 | 84 | override the ISA level}. |
252b5132 | 85 | |
6349b5f4 | 86 | @item -mgp32 |
ca4e0257 RS |
87 | @itemx -mfp32 |
88 | Some macros have different expansions for 32-bit and 64-bit registers. | |
89 | The register sizes are normally inferred from the ISA and ABI, but these | |
90 | flags force a certain group of registers to be treated as 32 bits wide at | |
91 | all times. @samp{-mgp32} controls the size of general-purpose registers | |
92 | and @samp{-mfp32} controls the size of floating-point registers. | |
93 | ||
94 | On some MIPS variants there is a 32-bit mode flag; when this flag is | |
95 | set, 64-bit instructions generate a trap. Also, some 32-bit OSes only | |
96 | save the 32-bit registers on a context switch, so it is essential never | |
97 | to use the 64-bit registers. | |
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98 | |
99 | @item -mgp64 | |
100 | Assume that 64-bit general purpose registers are available. This is | |
101 | provided in the interests of symmetry with -gp32. | |
102 | ||
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103 | @item -mips16 |
104 | @itemx -no-mips16 | |
105 | Generate code for the MIPS 16 processor. This is equivalent to putting | |
106 | @samp{.set mips16} at the start of the assembly file. @samp{-no-mips16} | |
107 | turns off this option. | |
108 | ||
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109 | @item -mips3d |
110 | @itemx -no-mips3d | |
111 | Generate code for the MIPS-3D Application Specific Extension. | |
112 | This tells the assembler to accept MIPS-3D instructions. | |
113 | @samp{-no-mips3d} turns off this option. | |
114 | ||
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115 | @item -mdmx |
116 | @itemx -no-mdmx | |
117 | Generate code for the MDMX Application Specific Extension. | |
118 | This tells the assembler to accept MDMX instructions. | |
119 | @samp{-no-mdmx} turns off this option. | |
120 | ||
6b76fefe | 121 | @item -mfix7000 |
9ee72ff1 | 122 | @itemx -mno-fix7000 |
6b76fefe CM |
123 | Cause nops to be inserted if the read of the destination register |
124 | of an mfhi or mflo instruction occurs in the following two instructions. | |
125 | ||
d766e8ec RS |
126 | @item -mfix-vr4120 |
127 | @itemx -no-mfix-vr4120 | |
128 | Insert nops to work around certain VR4120 errata. This option is | |
129 | intended to be used on GCC-generated code: it is not designed to catch | |
130 | all problems in hand-written assembler code. | |
60b63b72 | 131 | |
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132 | @item -mfix-vr4130 |
133 | @itemx -no-mfix-vr4130 | |
134 | Insert nops to work around the VR4130 @samp{mflo}/@samp{mfhi} errata. | |
135 | ||
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136 | @item -m4010 |
137 | @itemx -no-m4010 | |
138 | Generate code for the LSI @sc{r4010} chip. This tells the assembler to | |
139 | accept the @sc{r4010} specific instructions (@samp{addciu}, @samp{ffc}, | |
140 | etc.), and to not schedule @samp{nop} instructions around accesses to | |
141 | the @samp{HI} and @samp{LO} registers. @samp{-no-m4010} turns off this | |
142 | option. | |
143 | ||
144 | @item -m4650 | |
145 | @itemx -no-m4650 | |
146 | Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept | |
147 | the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop} | |
148 | instructions around accesses to the @samp{HI} and @samp{LO} registers. | |
149 | @samp{-no-m4650} turns off this option. | |
150 | ||
151 | @itemx -m3900 | |
152 | @itemx -no-m3900 | |
153 | @itemx -m4100 | |
154 | @itemx -no-m4100 | |
155 | For each option @samp{-m@var{nnnn}}, generate code for the MIPS | |
156 | @sc{r@var{nnnn}} chip. This tells the assembler to accept instructions | |
157 | specific to that chip, and to schedule for that chip's hazards. | |
158 | ||
ec68c924 | 159 | @item -march=@var{cpu} |
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160 | Generate code for a particular MIPS cpu. It is exactly equivalent to |
161 | @samp{-m@var{cpu}}, except that there are more value of @var{cpu} | |
162 | understood. Valid @var{cpu} value are: | |
163 | ||
164 | @quotation | |
165 | 2000, | |
166 | 3000, | |
167 | 3900, | |
168 | 4000, | |
169 | 4010, | |
170 | 4100, | |
171 | 4111, | |
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172 | vr4120, |
173 | vr4130, | |
174 | vr4181, | |
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175 | 4300, |
176 | 4400, | |
177 | 4600, | |
178 | 4650, | |
179 | 5000, | |
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180 | rm5200, |
181 | rm5230, | |
182 | rm5231, | |
183 | rm5261, | |
184 | rm5721, | |
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185 | vr5400, |
186 | vr5500, | |
252b5132 | 187 | 6000, |
b946ec34 | 188 | rm7000, |
252b5132 | 189 | 8000, |
963ac363 | 190 | rm9000, |
e7af610e | 191 | 10000, |
18ae5d72 | 192 | 12000, |
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193 | mips32-4k, |
194 | sb1 | |
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195 | @end quotation |
196 | ||
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197 | @item -mtune=@var{cpu} |
198 | Schedule and tune for a particular MIPS cpu. Valid @var{cpu} values are | |
199 | identical to @samp{-march=@var{cpu}}. | |
200 | ||
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201 | @item -mabi=@var{abi} |
202 | Record which ABI the source code uses. The recognized arguments | |
203 | are: @samp{32}, @samp{n32}, @samp{o64}, @samp{64} and @samp{eabi}. | |
252b5132 | 204 | |
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205 | @item -msym32 |
206 | @itemx -mno-sym32 | |
207 | @cindex -msym32 | |
208 | @cindex -mno-sym32 | |
209 | Equivalent to adding @code{.set sym32} or @code{.set nosym32} to | |
210 | the beginning of the assembler input. @xref{MIPS symbol sizes}. | |
211 | ||
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212 | @cindex @code{-nocpp} ignored (MIPS) |
213 | @item -nocpp | |
214 | This option is ignored. It is accepted for command-line compatibility with | |
215 | other assemblers, which use it to turn off C style preprocessing. With | |
216 | @sc{gnu} @code{@value{AS}}, there is no need for @samp{-nocpp}, because the | |
217 | @sc{gnu} assembler itself never runs the C preprocessor. | |
218 | ||
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219 | @item --construct-floats |
220 | @itemx --no-construct-floats | |
221 | @cindex --construct-floats | |
222 | @cindex --no-construct-floats | |
223 | The @code{--no-construct-floats} option disables the construction of | |
224 | double width floating point constants by loading the two halves of the | |
225 | value into the two single width floating point registers that make up | |
226 | the double width register. This feature is useful if the processor | |
227 | support the FR bit in its status register, and this bit is known (by | |
228 | the programmer) to be set. This bit prevents the aliasing of the double | |
229 | width register by the single width registers. | |
230 | ||
63bf5651 | 231 | By default @code{--construct-floats} is selected, allowing construction |
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232 | of these floating point constants. |
233 | ||
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234 | @item --trap |
235 | @itemx --no-break | |
236 | @c FIXME! (1) reflect these options (next item too) in option summaries; | |
237 | @c (2) stop teasing, say _which_ instructions expanded _how_. | |
238 | @code{@value{AS}} automatically macro expands certain division and | |
239 | multiplication instructions to check for overflow and division by zero. This | |
240 | option causes @code{@value{AS}} to generate code to take a trap exception | |
241 | rather than a break exception when an error is detected. The trap instructions | |
242 | are only supported at Instruction Set Architecture level 2 and higher. | |
243 | ||
244 | @item --break | |
245 | @itemx --no-trap | |
246 | Generate code to take a break exception rather than a trap exception when an | |
247 | error is detected. This is the default. | |
63486801 | 248 | |
dcd410fe RO |
249 | @item -mpdr |
250 | @itemx -mno-pdr | |
251 | Control generation of @code{.pdr} sections. Off by default on IRIX, on | |
252 | elsewhere. | |
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253 | |
254 | @item -mshared | |
255 | @itemx -mno-shared | |
256 | When generating code using the Unix calling conventions (selected by | |
257 | @samp{-KPIC} or @samp{-mcall_shared}), gas will normally generate code | |
258 | which can go into a shared library. The @samp{-mno-shared} option | |
259 | tells gas to generate code which uses the calling convention, but can | |
260 | not go into a shared library. The resulting code is slightly more | |
261 | efficient. This option only affects the handling of the | |
262 | @samp{.cpload} and @samp{.cpsetup} pseudo-ops. | |
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263 | @end table |
264 | ||
265 | @node MIPS Object | |
266 | @section MIPS ECOFF object code | |
267 | ||
268 | @cindex ECOFF sections | |
269 | @cindex MIPS ECOFF sections | |
270 | Assembling for a @sc{mips} @sc{ecoff} target supports some additional sections | |
271 | besides the usual @code{.text}, @code{.data} and @code{.bss}. The | |
272 | additional sections are @code{.rdata}, used for read-only data, | |
273 | @code{.sdata}, used for small data, and @code{.sbss}, used for small | |
274 | common objects. | |
275 | ||
276 | @cindex small objects, MIPS ECOFF | |
277 | @cindex @code{gp} register, MIPS | |
278 | When assembling for @sc{ecoff}, the assembler uses the @code{$gp} (@code{$28}) | |
279 | register to form the address of a ``small object''. Any object in the | |
280 | @code{.sdata} or @code{.sbss} sections is considered ``small'' in this sense. | |
281 | For external objects, or for objects in the @code{.bss} section, you can use | |
282 | the @code{@value{GCC}} @samp{-G} option to control the size of objects addressed via | |
283 | @code{$gp}; the default value is 8, meaning that a reference to any object | |
284 | eight bytes or smaller uses @code{$gp}. Passing @samp{-G 0} to | |
285 | @code{@value{AS}} prevents it from using the @code{$gp} register on the basis | |
286 | of object size (but the assembler uses @code{$gp} for objects in @code{.sdata} | |
287 | or @code{sbss} in any case). The size of an object in the @code{.bss} section | |
288 | is set by the @code{.comm} or @code{.lcomm} directive that defines it. The | |
289 | size of an external object may be set with the @code{.extern} directive. For | |
290 | example, @samp{.extern sym,4} declares that the object at @code{sym} is 4 bytes | |
291 | in length, whie leaving @code{sym} otherwise undefined. | |
292 | ||
293 | Using small @sc{ecoff} objects requires linker support, and assumes that the | |
294 | @code{$gp} register is correctly initialized (normally done automatically by | |
295 | the startup code). @sc{mips} @sc{ecoff} assembly code must not modify the | |
296 | @code{$gp} register. | |
297 | ||
298 | @node MIPS Stabs | |
299 | @section Directives for debugging information | |
300 | ||
301 | @cindex MIPS debugging directives | |
302 | @sc{mips} @sc{ecoff} @code{@value{AS}} supports several directives used for | |
303 | generating debugging information which are not support by traditional @sc{mips} | |
304 | assemblers. These are @code{.def}, @code{.endef}, @code{.dim}, @code{.file}, | |
305 | @code{.scl}, @code{.size}, @code{.tag}, @code{.type}, @code{.val}, | |
306 | @code{.stabd}, @code{.stabn}, and @code{.stabs}. The debugging information | |
307 | generated by the three @code{.stab} directives can only be read by @sc{gdb}, | |
308 | not by traditional @sc{mips} debuggers (this enhancement is required to fully | |
309 | support C++ debugging). These directives are primarily used by compilers, not | |
310 | assembly language programmers! | |
311 | ||
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312 | @node MIPS symbol sizes |
313 | @section Directives to override the size of symbols | |
314 | ||
315 | @cindex @code{.set sym32} | |
316 | @cindex @code{.set nosym32} | |
317 | The n64 ABI allows symbols to have any 64-bit value. Although this | |
318 | provides a great deal of flexibility, it means that some macros have | |
319 | much longer expansions than their 32-bit counterparts. For example, | |
320 | the non-PIC expansion of @samp{dla $4,sym} is usually: | |
321 | ||
322 | @smallexample | |
323 | lui $4,%highest(sym) | |
324 | lui $1,%hi(sym) | |
325 | daddiu $4,$4,%higher(sym) | |
326 | daddiu $1,$1,%lo(sym) | |
327 | dsll32 $4,$4,0 | |
328 | daddu $4,$4,$1 | |
329 | @end smallexample | |
330 | ||
331 | whereas the 32-bit expansion is simply: | |
332 | ||
333 | @smallexample | |
334 | lui $4,%hi(sym) | |
335 | daddiu $4,$4,%lo(sym) | |
336 | @end smallexample | |
337 | ||
338 | n64 code is sometimes constructed in such a way that all symbolic | |
339 | constants are known to have 32-bit values, and in such cases, it's | |
340 | preferable to use the 32-bit expansion instead of the 64-bit | |
341 | expansion. | |
342 | ||
343 | You can use the @code{.set sym32} directive to tell the assembler | |
344 | that, from this point on, all expressions of the form | |
345 | @samp{@var{symbol}} or @samp{@var{symbol} + @var{offset}} | |
346 | have 32-bit values. For example: | |
347 | ||
348 | @smallexample | |
349 | .set sym32 | |
350 | dla $4,sym | |
351 | lw $4,sym+16 | |
352 | sw $4,sym+0x8000($4) | |
353 | @end smallexample | |
354 | ||
355 | will cause the assembler to treat @samp{sym}, @code{sym+16} and | |
356 | @code{sym+0x8000} as 32-bit values. The handling of non-symbolic | |
357 | addresses is not affected. | |
358 | ||
359 | The directive @code{.set nosym32} ends a @code{.set sym32} block and | |
360 | reverts to the normal behavior. It is also possible to change the | |
361 | symbol size using the command-line options @option{-msym32} and | |
362 | @option{-mno-sym32}. | |
363 | ||
364 | These options and directives are always accepted, but at present, | |
365 | they have no effect for anything other than n64. | |
366 | ||
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367 | @node MIPS ISA |
368 | @section Directives to override the ISA level | |
369 | ||
370 | @cindex MIPS ISA override | |
371 | @kindex @code{.set mips@var{n}} | |
372 | @sc{gnu} @code{@value{AS}} supports an additional directive to change | |
373 | the @sc{mips} Instruction Set Architecture level on the fly: @code{.set | |
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374 | mips@var{n}}. @var{n} should be a number from 0 to 5, or 32, 32r2, 64 |
375 | or 64r2. | |
071742cf | 376 | The values other than 0 make the assembler accept instructions |
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377 | for the corresponding @sc{isa} level, from that point on in the |
378 | assembly. @code{.set mips@var{n}} affects not only which instructions | |
379 | are permitted, but also how certain macros are expanded. @code{.set | |
380 | mips0} restores the @sc{isa} level to its original level: either the | |
381 | level you selected with command line options, or the default for your | |
382 | configuration. You can use this feature to permit specific @sc{r4000} | |
383 | instructions while assembling in 32 bit mode. Use this directive with | |
ec68c924 | 384 | care! |
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385 | |
386 | The directive @samp{.set mips16} puts the assembler into MIPS 16 mode, | |
387 | in which it will assemble instructions for the MIPS 16 processor. Use | |
388 | @samp{.set nomips16} to return to normal 32 bit mode. | |
389 | ||
ec68c924 | 390 | Traditional @sc{mips} assemblers do not support this directive. |
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391 | |
392 | @node MIPS autoextend | |
393 | @section Directives for extending MIPS 16 bit instructions | |
394 | ||
395 | @kindex @code{.set autoextend} | |
396 | @kindex @code{.set noautoextend} | |
397 | By default, MIPS 16 instructions are automatically extended to 32 bits | |
398 | when necessary. The directive @samp{.set noautoextend} will turn this | |
399 | off. When @samp{.set noautoextend} is in effect, any 32 bit instruction | |
400 | must be explicitly extended with the @samp{.e} modifier (e.g., | |
401 | @samp{li.e $4,1000}). The directive @samp{.set autoextend} may be used | |
402 | to once again automatically extend instructions when necessary. | |
403 | ||
404 | This directive is only meaningful when in MIPS 16 mode. Traditional | |
405 | @sc{mips} assemblers do not support this directive. | |
406 | ||
407 | @node MIPS insn | |
408 | @section Directive to mark data as an instruction | |
409 | ||
410 | @kindex @code{.insn} | |
411 | The @code{.insn} directive tells @code{@value{AS}} that the following | |
412 | data is actually instructions. This makes a difference in MIPS 16 mode: | |
413 | when loading the address of a label which precedes instructions, | |
414 | @code{@value{AS}} automatically adds 1 to the value, so that jumping to | |
415 | the loaded address will do the right thing. | |
416 | ||
417 | @node MIPS option stack | |
418 | @section Directives to save and restore options | |
419 | ||
420 | @cindex MIPS option stack | |
421 | @kindex @code{.set push} | |
422 | @kindex @code{.set pop} | |
423 | The directives @code{.set push} and @code{.set pop} may be used to save | |
424 | and restore the current settings for all the options which are | |
425 | controlled by @code{.set}. The @code{.set push} directive saves the | |
426 | current settings on a stack. The @code{.set pop} directive pops the | |
427 | stack and restores the settings. | |
428 | ||
429 | These directives can be useful inside an macro which must change an | |
430 | option such as the ISA level or instruction reordering but does not want | |
431 | to change the state of the code which invoked the macro. | |
432 | ||
433 | Traditional @sc{mips} assemblers do not support these directives. | |
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434 | |
435 | @node MIPS ASE instruction generation overrides | |
436 | @section Directives to control generation of MIPS ASE instructions | |
437 | ||
438 | @cindex MIPS MIPS-3D instruction generation override | |
439 | @kindex @code{.set mips3d} | |
440 | @kindex @code{.set nomips3d} | |
441 | The directive @code{.set mips3d} makes the assembler accept instructions | |
442 | from the MIPS-3D Application Specific Extension from that point on | |
443 | in the assembly. The @code{.set nomips3d} directive prevents MIPS-3D | |
444 | instructions from being accepted. | |
445 | ||
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446 | @cindex MIPS MDMX instruction generation override |
447 | @kindex @code{.set mdmx} | |
448 | @kindex @code{.set nomdmx} | |
449 | The directive @code{.set mdmx} makes the assembler accept instructions | |
450 | from the MDMX Application Specific Extension from that point on | |
451 | in the assembly. The @code{.set nomdmx} directive prevents MDMX | |
452 | instructions from being accepted. | |
453 | ||
1f25f5d3 | 454 | Traditional @sc{mips} assemblers do not support these directives. |